1. Field of the Invention
The present invention relates to a method of making collectively a plurality of device chips, in particular micromirror chips, from a single material substrate.
2. Description of the Related Art
For achieving better production efficiency and lower cost, a plurality of identical devices (micromirror chips, semiconductor laser units, etc.) may be produced collectively from a single material substrate than produced individually from the corresponding number of material substrates. Japanese patent application-A-6(1994)-275714, for example, discloses a method by which several semiconductor laser units are formed in a single material substrate, the substrate being divided later into smaller pieces to provide the end products.
FIGS. 12A-12E of the accompanying drawings illustrate the principal steps of the above-mentioned conventional method. In accordance with it, a prescribed number of semiconductor laser units are formed in a common material substrate 1. As shown in FIG. 12A, the substrate 1 is provisionally attached to a glass disk 2 by adhesive 3 and polished. Then, as shown in FIG. 12B, a resist layer 4 is formed to cover the upper surface of the substrate 1, and grooves 5 are formed in the resist layer 4 by etching. As shown in FIG. 12C, electrodes 6a are formed on the substrate 1 for the respective semiconductor laser units. Finally, as shown in FIG. 12D, the substrate 1 is divided at positions corresponding to the division-facilitating grooves 5. Thus, individual semiconductor laser units as shown in FIG. 12E are obtained.
By the conventional method, the division-facilitating grooves 5 are formed after the basic structure of the laser units has been built in the material substrate 1. Unfavorably, such a procedure impairs the production efficiency due to the extra step of forming the grooves.